Magnetic pick-up device



March Z1, 1961 F. BUDRECK 2,976,075

MAGNETIC PICK-UP DEVICE Filed July 17. 1959 60 [8.7475 '76 54 5g gl 4 A'rTY.

INVEN TOR. FRANCES BuoRacK United States Patent O MAGNETIC PICK-UP DEVICE Frances Bndreck, Chicago, Ill., assignor to Monarch Tool & Machinery Co., Chicago, Ill., a corporation of Illinois Filed July 17, 1959, Ser. No. 827,813

6 Claims. (Cl. 294-655) The present invention relates to quick-release magnetic pick-up devices and has particular reference to a small, compact, manually operable magnetic pick-up device or lifter by means of which a small object of a group of such objects may be brought within the magnetic field of a permanent magnet associated with the device and thus attracted to the body of the magnet. magnetic sheet or membrane is interposed between the magnet and the object or groupof objects and is adapted to be pushed away from the magnet to thus force the attracted object or objects out of the magnetic field, thus releasing them. Hand operated lifters of this general character are known and are employed where the load to be lifted is not large. Otherwise, for large loads, power actuated mechanisms of this sort have been devised.

It is among the principal objects of the present invention to provide a lifter assembly of this general character having associated therewith novel means for automatically concentrating the magnetic flux when the device is in condition to attract an object for lifting purposes with the non-magnetic membrane in close proximity to the body of the magnet so that a greater lifting power or pull will be exerted upon an object than otherwise, the flux-concentrating means being rendered ineffective almost immediately as the membrane is pushed away from the magnet body toward its position of release so that the flux concentration is immediately dispersed and the object quickly released.

Another and important object of the invention, in a -quick-release lifterof this general character is to embody such flux-concentrating means in a magnet assembly having high coercive value and a relatively large magnetic area so that increased attractive power is offered in the case of a single magnetic objectY which isto be lifted while increased pick-up capacity is offered in the case of multiple 'articles in bulk.

In carrying out this last mentioned object, the invention contemplates the use of a specially desgined magnet of the mixed ferrite type, commonly referred to as a ceramic magnet. Such magnets are a comparatively recent development in the field of permanent magnet construction and they possess greatly improved magnetic properties over magnets `which are constructed of metallic alloys. One such magnetic material of the mixed ferrous` type is known as Indox a development of the Indiana Steel VProducts Company of Valparaiso, Indiana. This` barium-ferrite material is characterized by the fact that it is electricallynon-conductive, is extremely resistant to demagnetizing influences, evidences low eddy current losses, exhibits a high coercive force, has a low remanence and high permeability. Because of these characteristics, of this magnetic material, the magnetic length thereof-need be but a fraction of that required for the ferrous alloys in attaining the same magnetic pull for a given size magnet. Where barium-ferrite ceramic materials are concerned, magnetic stability is pronounced f and permanent magnets constructed of this material main- Vtain their magnetic strength despite weakening influences A thin, non# Patented Mar. 21, 1961 such as contact with extraneous magnetic fields and frequent removal and replacement of the magnetic armatures. Additionally, such material is relatively light as compared with magnetic metallic alloys.

It is a still further object of the invention to provide a quick-release magnetic lifter or pick-up device employing a permanent magnet assembly, the magnet proper of which is constructed of ceramic material as outlined above and which is in the `form of a fiat wafer or disk, the disk being magnetized in the direction of its smallest dimension so that the opposite faces thereof present magnetic poles of opposite polarity. A backing plate of magnetic material which is in face-to-face contact with one of the pole faces presents an annular marginal flange which encircles the magnet disk but is spaced therefrom so as to provide a low reluctance path for magnetic ux extending from the rear face of the magnet toward the forward face thereof. This marginal flange in combination with such forward face, establishes an air gap. The magnet assembly is movable within a holder including a mild steel flux-concentrating ring and, when the magnet assembly is in its retracted position of release, the same is remote from the ring so that the latter is not magnetized and possesses no pick-up or lifting ability. When the magnet assembly is moved to an advanced lifting position, the mild steel ring and the annular flange of the backing plate move into mutual contact to thus increase the length of the iron content of the magnetic circuit and to decrease the'air gap and concentrate the ux in the vicinity of the air gap. A non-magnetic membrane extends across the forward rim of the steel ring and at the Sametime that the annular magnet-.encircling flange and steel ring move into contact, the forward face of the magnet moves into close proximity to the membrane whereby the flux path is through the membrane so that an object or objects on the side of the membrane remote from the magnet will be attracted toward the forward face of the latter and against Ythe membrane. When the magnet assembly is moved to its retracted position, not only does the membrane serve to push the articles out of the sphere of influence of the magnetic field, but the magnet encircling flange and steel ring become separated, thus collapsing the magnetic field in the vicinity of the air gap and exerting a demagnetizing effect upon the object or objects which are thus immediately released. The non-magnetic membrane, in addition to serving its function of exerting a physical repelling thrust upon the object additionally functions as a seal to exclude extraneous magnetic particles or dirt from being attracted into the air gap established between the magnet-surrounding flange and the rim of the magnet, as well as protecting the forward face of the magnet from injury.

The provision of a quick-release magnetic lifter or pick-up device which is extremely simple in its construction and which therefore is not costly to manufacture; one which is comprised of a minimum number of moving parts and which therefore is unlikely to get out of order; one which is small, compact and of light weight construction, considering its lifting capacity; one which is capable of ease of assembly and disassembly for purposes of inspection or replacement of parts; and one which is otherwise well adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

Numerous other objects' and advantages of the invention, not at this time enumerated, will become readily apparent as the following description ensues.

In the accompanying single sheet of drawings forming a part of this specification, a preferred embodiment of the invention has been shown.

Fig. l is a perspective view of a releasable permanent magnet holding or pick-up device constructed in accordance with the principles of the present invention;

Fig. 2 is a bottom plan view of the structure shown in Fig. l;

Fig. 3 is a sectional view taken substantially on the vertical plane indicated by the line 3 3 of Fig. l in the direction indicated by the arrows;

Fig. 4 is a sectional view similar to Fig. 3, showing the device in its position of release; and

Fig. 5 is a sectional view taken substantially along the line 5--5 of Fig. 3.

Referring now to the drawing in detail where a preferred form of the invention has been shown, the releasable holding or pick-up device has been designated in its entirety at and involves in its general organization a generally cylindrical, inverted cup-shaped casing 12 which may be formed of any suitable non-magnetic material but which preferably is formed of Lucite, or other suitable thermoplastic or thermosetting moldable plastic. The casing 12 includes a top wall 14 from which there depends a cylindrical marginal annular flange or side wall 16 presenting a lower continuous marginal rimy 18. The top Wall 14 is provided with a central opening 20 therethrough and through which opening there projects the reduced stem portion 22 of a plunger 24, the plunger being coaxial with the cylindrical casing 12. The lower end of the stem portion 22 of the plunger 24 carries a magnet assembly which has been designated in its entirety at 26 and the nature and function of which will be set forth presently. The plunger 24 is normally maintained in an elevated position such as has been illustrated in Fig. 3 so that the magnet assembly 26 is maintained in contact with the top wall 14 and in such a position that it is remote from the rim 18 of the side wall 16. The plunger 24 and magnet assembly 26 carried thereby are movable bodily as a unit between the retracted position thereof and an advanced position such as has been illustrated in Fig. 4 wherein the magnet assembly is in close proximity to the rim 18 of the side wall 16.

Accordingly, a compression spring 30 surrounds the stem portion 22 of the plunger 24 and bears at its lower end against the top wall 14. The upper end of the spring 30 bears against an annular shoulder 32 afforded between the reduced stem portion 22 and the body portion of the plunger 24.

Engagement ofthe magnet assembly 26 with the underneath or inside wall 14 limits the upward movement of the plunger 24. The upper end of the plunger 24 carries a manipulating knob 34 having a threaded socket 36 formed therein designed for threaded reception on a post 38 provided on the extreme upper end of the plunger. The spring 30 is enclosed within a relatively tall cylindrical boss 40 which is formed on the upper side of the top wall 14 and which surrounds the spring. The upper end of the boss 40 is exteriorly threaded as at 42 for threaded reception thereover of a reaction member 44 having laterally extending arms or protuberances 46 designed for engagement with the middle and index fingers of the user during manipulation of the device in a manner that will be described subsequently.

The magnet assembly 26 includes a backing plate or base 50 in the form of a thin circular disk which constitutes a protective backing wall having a continuous marginal flange 52 projecting downwardly from the rim of the disk. The disk S0 and its marginal flange thus, in effect, form a shallow inverted cup-shaped structure designed for reception therein of a magnet proper 54. The stem portion 22 of the plunger 24 is riveted as at 55 to the central region of the disk 50. The magnet 54 is in the form of a wafer-type flat ceramic ring of relatively large area but having a relatively short magnetic length. Preferably the magnet is of the barium ferrite type. The magnet 54 is magnetized in an axial direction to produce upper and lower faces 56 and 58 respectively which are of opposite polarity as indicated by the legending in Figs. 3 and 4. The face 56 of the magnet 54 is secured to the underneath side of the backing plate or disk 50 by a suitable adhesive which may be in the form of an air drying glue such as Pliobond, a product of the Goodyear Tire and Rubber Company, EC-1428, a product of Minnesota Mining and Manufacturing Company, or any one of numerous cements such as Versamid, a product of General Mills Corporation, or Epon 828, a product of Shell Chemical Corporation. The thickness of the magnet 54 is slightly greater than the height of the annular side wall S2 so that the magnet projects slightly beyond the rim 60 of the side wall 52, with the annular face 58 thereof lying slightly below the plane of the rim 60. The overall diameter of the magnet 54 is slightly less than the internal diameter of the side wal152 so that a small annular air gap 62 exists between the rim 60 and the pole face 58 of the magnet 54. The magnet assembly is ex tremely compact and the lower rim regions of the assembly in the vicinity of the air gap 62 presents a relatively powerful attractive force on any ferromagnetic article or armature which may be encountered by the magnetic eld in the vicinity of such air gap.

The rim 18 of the casing side wall 16 is recessed internally as at 70 and a mild steel ring 72 seats within the recess 70 and is fixedly secured therein. 'Ihe ring 72 is generally cylindrical and presents a downwardly facing rim surface 74 the nature and function of which will be set forth presently. The ring 72 is recessed internally to provide a groove 75 in which there is nested the rim or edge region of a non-magnetic combined closure member and armature seat 76 which may be in the form of a thin disk of a suitable transparent plastic material.

The internal diameter of the ring 72 is substantially equal to the external overall diameter of the cylindrical wall so that when the plunger 24 and magnet assembly 26 assume the advanced position wherein they are illustrated in Fig. 4, the side wall 52 is nested within the ring 72 and is preferably in physical sliding contact therewith while at the same time the underneath face of the magnet 54 bears against the non-magnetic bottom wall or closure member 76 as clearly shown in Fig. 4.

In the advanced position of the magnet as shown in Fig. 4, the soft ring 74 projects forwardly a slight distance beyond the front face of the magnet and, in cornbination with this latter face, establishes an extension of the air gap 62 while at the same time serving to concentrate the flux in the magnetic circuit in the narrow rim 74 so that upon encountering a magnetic article or armature, the latter will be drawn to the surface 74 with an extremely high degree of pull.

Movement of the magnet assembly 26 to its advanced position of operative register with rthe mild steel ring 72 against the yielding action of the spring 30 may be effected conveniently by hooking the middle and index fingers beneath the radial protuberances 46 for reaction purposes, and forcing the knob 34 downwardly toward the member 44 by means of the thumb. Upon release of the knob 34, the spring 30 will urge the plunger upwardly to move the magnet assembly to the retracted position wherein it is shown in Fig. 3 with the magnet removed an appreciable distance from the ring 72. The ring 72 will thus become demagnetized and lose its attractive power. The ring 72 thus is, in effect, in the nature of an annular pole piece which, when in contact with the side wall 52 assumes the polarity of the magnet face 58 and which, when the armature is retracted, loses its polarity.

In the operation of the device 1t), with the magnet assembly 26 in its advanced positon as shown in Fig. 4, a magnetic article or a series of loose magnetic articles to be picked up will be attracted according to the laws of magnetism to the polarized underneath face of the magnet and especially to the rim 74 of the nng 72 where the epreuve magnetic ilux is highly concentrated. If the article possesses a flat face capable of vbeing engaged coextensively with the rim 74 an extremely powerful pulling will be Iexerted upon such article. Small articles will tend to move toward the air gap 62 but they may also adhere to the underneath face of the non-magnetic bottom wall vI6 due to the attractive forces exerted upon them. The strength of the spring 30 is such that the upward force exerted upon the plunger 24 when the latter is in its fully advanced position is in excess of that required to move the magnet assembly 26 away from the article or the magnetic objects attracted to the magnet so that as the plunger and magnet move away yfrom the bottom wall 76 the article or articles are Iforced out of the magnetic field of iniluence of the magnet, i.e. out of the path of magnetic flux, whereupon it or they will be released.

While one specific form of holding magnet assembly or releasable pick-up device constructed in accordance with the principles of the present invention has been shown and described herein for illustrative purposes, it will be understood that this `form ofthe invention does not by any means indicate the only form suitable for the functions intended. The illustrated form is merely one which has claim and brane substantially coplanar with the rim and extending transversely across the same, a thin permanent magnet of :the mixed ferrite type mounted for axial shiftin-g move- :ment within said casing and presenting a planar forward :face, said magnet being magnetized in an axial direction whereby the forward and rear faces thereof constitute -magnetic poles of opposite polarity, a combined backing plate for the magnet including a backing wall in co .extensive contact with the rear face of the magnet and 'a forwardly extending marginal flange encompassing the jpenipheral edge of the magnet and slightly spaced therefrom, said marginal flange terminating in a plane par- `allel to and in close proximity to the forward face of the rmagnet, said backing plate and flange being formed of magnetic material, said magnet and backing plate being :shiftable between an advanced position wherein theforward pole face of the magnet is in llush engagement with :said membrane and a retracted position wherein said jpole face is remote from said membrane, and means for :shifting said magnet between 'its advanced and retracted positions.

2. In a releasable magnetic pick-up device, the combination set forth in claim l including, additionally,

:spring means normally biasing said magnet toward its Aretracted position.

3. A magnetic pick-up device comprising in combination a tubular casing formed of non-magnetic material, a rear Wall closing the rear end of the casing, a thin non- Amagnetic membrane extending across the -forward end of 'the casing coplanar with the rim thereof and closing the 'forward end of the casing, a thin -permanent magnet of the mixed ferrite type mounted 4for axial shifting movement within said casing and presenting a planar forward tface, said magnet being magnetized in an axial direction whereby the forward and rear faces thereof constitute magnetic poles of opposite polarity, a combined backing vplate for the magnet including a backing Wall in coextensive contact with the rear face of the magnet and a forwardly extending marginal flange encompassing the peripheral edge of the magnet and slightly spaced therefrom, said marginal ange terminating in a plane parallel to and in close proximity to the -forward face of the magnet, said backing plate and flange being formed of magnetic material, said magnet and backing plate being shifta'ble within the casing 'between 'an advanced position wherein the forward pole face Vof the magnet is in flush engagement with said membrane and a retracted position wherein said pole face is remote from said membrane, a plunger coaxial with the casing and having its inner end secured to said backing plate, said plunger projecting through said rear wall and being slidable therein, a coil spring surrounding the plunger and having one end bearing against a downwardly Ifacing shoulder on the.

plunger and having its other end elfectively bearing against said rear wall and serving to normally urge said plunger rearwardly of the casing whereby said magnet is normally biased toward its retracted position.

4. A releasable magnetic pick-up device comprising in combination a tubular casing `formed of non-magnetic material and presenting a forward rim, a thin membrane substantially coplanar with the rim and extending transversely across the same, a thin permanent magnet of the mixed ferrite type mounted for axial shifting movement within said casing and presenting a planar forward face, said magnet being magnetized in an axial direction whereby the `:forward and rear faces thereof constitute magnetic poles of opposite polarity, a combined backing plate for the magnet including a backing wall in ooextensive contact with the rear face of the magnet and a forwardly extending marginal flange encompassing the peripheral edge of the magnet and slightly spaced therefrom, said marginal flange terminating in a plane parallel to and in close proximity to the forward face of the magnet, said backing plate rand flange being `formed of magnetic material, a ring of magnetic material mounted on the forward rim region of said casing and positioned in the path of movement of the annular ilange of said backing plate, said magnet and backing plate being movable within the casing between an advanced position wherein said annular flange coextensively engages said ring, and means for shifting said magnet between its advanced and its retracted positions.

5. A releasable magnetic pick-up device comprising in combination a tubular cylindrical casing formed of nonmagnetic material, a rear wall closing the rear end of the casing, a thin non-magnetic membrane extending across the forward end of the casing substantially coplanar with the rim thereof, and closing the forward end of the casing, `a permanent magnet assembly slidable within the casing between said rear wall and membrane, said magnet assembly comprising a thin circular disk-like permanent magnet proper formed of barium ferrite and magnetized in an axial direction whereby the forward and rear faces thereof constitute magnetic poles 'of opposite polarity, said forward and rear yfaces being flat and extending in parallelism with the magnet being coaxial with the casing, a cup-shaped retainer and backing plate for the magnet and having a flat circular bottom wall and a forwardly extending continuous marginal flange, said magnet being seated within said retainer with its rear pole face in coextensive contact with the retainer bottom wall and with the marginal flange encompassing the magnet and slightly spaced from the periphery thereof, said cupshaped retainer being formed of magnetic material, the forward rim of said annular flange lying in a plane which is parallel to and spaced a slight distance rearwardly of the plane of the forward magnet pole face, a ring of magnetic material mounted on the forward rim region of said casing and coaxial with the magnet and annular flange, the internal diameter of said ring being substantially equal to the external flange, said magnet assembly being movable between an advanced position wherein the annular flange is in telescopic physical cont-act with the ring, thus providing a low reluctance path through the magnet, retainer and ring and a high reluctance path across the annular air gap existing between the ring and forward peripheral edge region of the magnet, and a retracted position wherein said tlange is out of contact with the ring and the latter is demagnetized, and

means for shifting said magnet assembly between its retracted `and its advanced positions.

6. In a releasable magnet pick-up device, the combination set forth in claim 5 wherein said shifting means cornprises a plunger coaxial with the casing and projecting slidably through Said rear wall, the inner end of the plunger being Koperatively connected to said magnet assembly, a tubular boss on said rear Wall and surrounding said plunger exteriorly of the casing, a spring surrounding said plunger withjn the boss and effectively interposed between oppositely facing surfaces on the plunger and casing respectively for normally urging said magnet toward its retracted position, and cooperating linger-en-` gaging protuberances on said plunger and tubular boss to facilitate axial shifting of the plunger relative `tothe casing.

References Cited in the tile of this patent UNITED STATES PATENTS 2,417,762 Koller Mar. 18, 1947 2,790,116 Kirby Apr. 23, 1957 FORElGN PATENTS 929,300 Germany June 23, 1955 

